Hyperthyroidism in Cats

Hyperthyroidism is a common endocrine disorder in middle-aged and older cats characterized
by overproduction of thyroid hormones. Hyperthyroidism is excessive production and
secretion of thyroid hormones from an abnormally functioning thyroid gland. It is the
most common endocrine disorder of cats. which leads to an increased metabolic rate.
Etiology
– Most cases are caused by benign tumors (adenomas) of the thyroid gland.
– Less commonly, malignant tumors (carcinomas) may be involved.
– The exact cause is unknown but may involve environmental factors and genetics.
Common Signs & Clinical Features
– Weight loss despite increased appetite (polyphagia)
– Increased activity, restlessness, or hyperactivity
– Tachycardia (fast heart rate)
– Vomiting or diarrhea
– Poor coat condition or hair loss
– Increased thirst and urination
– Enlarged thyroid gland which can be visible in some cases
– Elevated blood pressure
– Behavioral changes: increased vocalization, agitation

Diagnosis
– Physical exam: Palpable enlarged thyroid gland or asymmetry in some cases
– Blood tests:Elevated serum total T4
– **Additional tests:**
– Free T4 (FT4) by equilibrium dialysis (more sensitive but costly test)
– Total T3 (less commonly used) but can be diagnostic in many cases
– Blood pressure measurement
– Blood work for kidney and liver function (as hyperthyroidism can affect these organs)
– Imaging (ultrasound ) if needed for localization or to assess for carcinoma in selective cases.
Treatment Options
1. Medication:
– Methimazole (Felimazole):Oral tablets or topical gel to inhibit thyroid hormone synthesis
2. Radioactive Iodine Therapy (I-131):
– The gold standard; selectively destroys overactive thyroid tissue
– Usually performed at specialized centers (need referral)
3. Surgical Removal:

– Thyroidectomy; less common now due to radiation therapy availability
4. Diet:
– Prescription diets (e.g., Hill’s y/d) that limit iodine intake to reduce hormone production
Prognosis**
– Many cats respond well to treatment with medication or radioactive iodine.
– Radioactive iodine offers a permanent solution and can cure hyperthyroidism in most cases.
– Regular monitoring is essential to adjust treatment and manage potential complications, such
as kidney disease, which may become apparent once thyroid levels are controlled.
Important Considerations
– Monitoring: Regular blood tests (every 6-12 months or as recommended).
– Complications: Untreated hyperthyroidism can cause heart disease, high blood pressure, and
weight loss.
– Concurrent Diseases: Many hyperthyroid cats develop kidney disease; treatment may unmask
underlying renal issues, so careful monitoring is essential.
Please call Groat Veterinary centre , a “cat clinic” if your furry friend is exhibiting any of the signs
mentioned above.